1. Field of the Invention
The present invention relates to a molded case circuit breaker, and more particularly, to a molded case circuit breaker having a contact on mechanism.
2. Description of the Background Art
In general, a molded case circuit breaker is a protective electrical device to protect an electrical load equipment and an electrical line from an overload or overcurrent which may occur in an electrical circuit, by automatically breaking the electrical circuit. In such molded case circuit breaker, a position of a handle, which is manually manipulated by a user, may be divided into a mechanism release position by a switching mechanism (i.e., a TRIP position), a circuit opening position (i.e., an OFF position, in other words RESET position), and a circuit closing position (i.e., an ON position). When a fault current (or an abnormal current, etc.) occurs, the molded case circuit breaker performs a trip operation, and the handle indicates another position, except the on position. Meanwhile, due to a contact melt-adhered state of a movable contactor and a fixed contactor or any other reasons, when the contacts of the movable contactor and the fixed contactor are not separated from each other, a user manipulates the handle to move its position to the reset position, i.e., off position, such that the handle is moved to the on position or a position towards the on position indicating and warning to a user that the molded case circuit breaker is conducted. Here, the handle would automatically indicate the on position or a position near the on position, without indicating the off position (without being in the off position), thereby notifying the user of a conducted state in which the contacts of the movable contactor and the fixed contactor are currently contacted to each other. Such operation (function) is referred to as a “contact on operation (function).” The present invention is to provide a molded case circuit breaker having a mechanism performing the “contact on operation.”
In order to implement the contact on operation in which the handle automatically indicates the on position when the contacts are contacted and thusly in the conducted state, a position of a toggle pin serving as a connection means between an upper link and a lower link should not go beyond a position of a hinge point (i.e., a pivot) of a lever for rotatably supporting the handle. Here, the upper and lower links serve as a drive unit connected between a shaft for supporting and driving the movable contactor and the handle. That is, when viewed at the front, the toggle pin should be positioned at a left side of the hinge point (pivot). Meanwhile, in the tripped state, the position of the toggle pin should go beyond the position of the lever hinge point, i.e., at a right side of the hinge point. Accordingly, such respective positions during the contact on operation and in the tripped state are opposite.
In order to implement both the contact on operation and the trip operation, there is a need to adjust the position of the bending point between the upper link and the lower link as well as length ratio between the upper link and the lower link. Accordingly, there may be a structural problem of causing unstableness of the switching mechanism so as to satisfy the condition of the opposite positions.
In addition, a method for preventing the handle from going towards the off position by installing a stopper so as to restrict the lever may be proposed. Here, the handle would be stopped near the off position, not exactly at the off position. This may cause a problem of not performing the contact on operation when the contacts are contacted and thusly in the conducted state.